1. Field of the Invention
This invention relates to a structure of a silicon valve.
2.Prior Art
An article entitled "Fabrication of Novel Three-Dimensional Microstructures by the Anisotropic Etching of (100) and (110) Silicon", by E. Bassous, IEEE Transactions on Electron Devices, Vol. ED-25, No. 10, October 1978, pages 1178-85 teaches the use of anisotropic etching of single crystal silicon to make ink jet nozzles, optical waveguides, multisocket miniature electrical connectors and electromechanical devices.
U.S. Pat. Nos. 4,157,935 issued to Solyst and 4,455,192 issued to Tamai teach methods of forming an ink jet nozzle array by chemical etching of a silicon wafer.
It is also known to fabricate conventional metal fluid metering valves such as those using matched fittings of very precisely machined metal components. Typical tolerances of the lapped machine parts are in the millionths of an inch. This is a complicated, labor-intensive, time-consuming manufacturing process yielding components which are expensive and subject to reliability problems as the internal tolerances change due to wear and exposure to fuel and fuel contaminants. It would be desirable to fabricate fuel injectors and other valves with substantially less labor and time using a significantly less complicated manufacturing process. That is, superior tolerances are desirable as in an insensitivity to fuel contaminants and improved reliability.
Further, it is also known to use a silicon valve for controlling the flow of fluid using first and second silicon members. The first silicon member is generally planar and has an orifice for passing the fluid. The second silicon member has a planar silicon surface aligned with, and relatively moveable to, the orifice for selectively opening and closing the orifice thereby controlling flow of fluid through the orifice. Such a silicon valve and method for fabricating it are further described in U.S. Pat. Nos. 4,628,576 issued Dec. 16, 1986 and 4,647,013 issued Mar. 3, 1987, both assigned to the assignee hereof.
U.S. Pat. No. 1,243,122 discloses a valve which is used to vaporize a gasoline and air mixture as the mixture leaves the carburetor of an engine. FIG. 1 of that patent illustrates the valve comprising perforated plates 10, 12 positioned to receive the gasoline and air mixture from the carburetor 6. The plates 10, 11 are normally held against one another with the perforations in each plate offset to block any flow through the valve. When a partial vacuum is formed in manifold 5, the plate 12 moves away from the fixed plate 10 thereby vaporizing the fuel mixture as seen in FIG. 3 of that patent. This reference neither teaches nor suggests the use of silicon to construct a valve.
U.S. Pat. No. 4,538,642 discloses a valve which, as seen in FIG. 1, includes an electrically conductive sheet-like member 4 provided with an electrically insulative face surface 6 and an array of apertures 7-11. A second electrically conductive sheet-like member 12 abuts the first member 4 at face surface 6 to close off apertures 7-11. The second sheet-like member 12 has apertures 16-13 which are non-aligned with the apertures 7-11. To open the valve, switch 28 is closed, causing electric current to pass through member 4, then through conductor 26, and then through member 12 to produce opposing electromagnetic fields to raise the sheet members 4, 6 as seen in FIG. 3. Again, there is no teaching or suggestion of using silicon to construct the valve.
The above prior art has shown that precise control of fluid flow, including gaseous, liquid or vacuum, is very difficult to achieve. The conventional approach using metal valve systems requires precise machining on very small components. Valve to valve variability is very difficult to control and the total operation is very expensive. These metal valves usually include a metal housing and pintle and are susceptible to clogging by very small foreign matter introduced through the fluids. Other approaches now in use include injection molding of a plastic valve seat against which a rubber-tipped plunger is forced to effect closure. This type of valve is subject to sticking due to environmental conditions such as very low temperature. Simpler actuation and improved flow control of silicon valves would also be desirable. These are some of the problems this invention overcomes.